Our studies have concerned the metabolic errors of glutathione synthesis and degradation (glutathionuria, glutathione synthase deficiency and gamma glutamyl-cysteine synthase deficiency), cystinosis, homocystinuria, and phenylketonuria. Patients studied with the abnormalities of glutathione synthase include patients with severe acidosis (oxoprolinuria) and the adult-non-acidotic form of this disorder. We have demonstrated that glutathionuric patients have a deficiency of the enzyme gamma glutamyl transpeptidase, but appear to have normal amino acid transport in fibroblasts and kidney despite this enzyme deficiency. The molecular lesions in the acidotic and non-acidotic forms of glutathione synthase deficiency has been distinguished and partially characterized. Our studies on cystinosis have revealed a consistent defect in thyroid function, and a controlled clinical trial of high dose vitamin C in this lethal disorder is continuing. A new form of phenylketonuria due to biopterin deficiency has been characterized and an in vivo radiochemical assay for phenylalanine hydroxylase developed. BIBLIOGRAPHIC REFERENCES: Schulman, J.D.: Diagnostic value of amniocentesis and analysis of amniotic fluid and its cellular constituents. In Ayromlooi, J. (Ed.): Scientific Basis Obstetrics and Gynecology. Pahlavi Press, 1977, in press. Schulman, J.D.: Inborn errors of sulphur metabolism. Crawford, J.D. (Ed.) Harvard University Press, 1977, in press.